The warning that we could face rolling blackouts in Greater Boston in a couple years would seem like bad news to most of us.

But for New Hampshire Transmission, it represents a major opportunity.

The Seabrook, N.H.-based subsidiary of NextEra Energy is trying to build support for a proposed underwater power line that would bring 520 megawatts of power from southern New Hampshire into the Boston area. The underwater portion of the 68-mile line would be 50 miles long, leaving the shore in Salisbury and making landfall in Lynn, passing Cape Ann along the way.

NHT’s SeaLink proposal is currently competing for attention at grid operator ISO New England’s headquarters with another proposal from National Grid and Northeast Utilities that consists of new transmission lines into and within Greater Boston. NHT officials hope ISO New England will make a decision this fall.

NHT President Matt Valle tells me his firm’s proposal is superior to the rival plan because it could be permitted and constructed at a faster pace, and without the community impacts that overhead power lines can create. The underwater cable would also be more reliable, he says, than overhead lines during times of extreme weather. The cable would be buried beneath the seabed for its underwater route, and would follow an abandoned railroad bed and partially completed bike path from the Lynn shoreline to the Mystic substation in Everett.

“The situation is clearly urgent,” Valle says. “When we’re talking about the potential for rolling blackouts for 3 million people, this becomes a public (concern).”

NHT first proposed its alternative to the Northeast Utilities/National Grid projects in 2012, according to ISO New England spokeswoman Marcia Blomberg. These transmissions projects, because they address reliability concerns, would be funded by New England ratepayers through the electricity market that ISO New England oversees.

Blomberg says Holyoke-based ISO New England is still weighing the two proposals, with an eye toward developing the most cost effective and reliable transmission solution. An ISO presentation in June shows the SeaLink option to be the more expensive of the two, with estimated unique costs of $804 million, compared to $450 million for the rival proposal. (The proposals, as they’re measured by ISO New England, also share an additional $221 million in common transmission upgrades.)

However, Valle says this comparison doesn’t take into account the avoidance of congestion charges and other benefits from getting a project in service more quickly to address Greater Boston’s pressing grid reliability issues.

The SeaLink project was proposed before ISO New England warned in December about the potential for rolling blackouts for the Northeast Massachusetts-Boston area at times of peak electricity demand if a natural gas plant proposed for Salem isn’t built by June 2016. It’s now clear that the power plant will miss the deadline, adding a sense of urgency to NHT’s proposal. (ISO New England would also consider other solutions, such as using temporary diesel generators, before controlled outages would be used.)

SeaLink won’t be done by the June 2016 deadline, but Valle says it could still be completed more quickly than the competing alternative. If ISO New England approves the SeaLink plan this fall, permitting would take a little over a year, and construction could start on SeaLink in 2016, in time to put the project in service by 2018. With the Salem power plant’s fate unclear and no other major plants on tap for construction in the region, we may need the extra transmission even more at that point than we would in 2016.

Update (8/20): I reached out to National Grid and Northeast Utilities to get their perspective on the SeaLink project yesterday. I heard back from an NU spokesman today, after this story had published. He argued in favor of the NU/Grid plan, saying it is superior to NextEra's because the cost is considerably lower for consumers, repairs on a land-based transmission line are much easier to make in the event of an outage, the project allows for more electricity system expansion options, and it's more environmentally friendly because it uses existing rights-of-way.